1. Field of the Invention
This invention relates to air filters and, more particularly, to an air filter assembly for a heavy duty motor vehicle generator. The air filter assembly is intended to have particular application to a heavy duty motor vehicle generator which is operating in a dust-laden environment.
2. Description of the Prior Art
Motor vehicle generators (the term "generator" as used herein includes alternators) and, particularly, heavy duty motor vehicle generators typically include air flow passages which permit cooling air to flow through the generator. A fan coupled to a belt-driven pulley is conventionally provided at one end of the generator to draw cooling air therethrough. The end of the generator opposite the fan usually includes rectifier means and one or more heat sinks for dissipating heat build-up in the rectifiers. An apertured plate (which may include the aforementioned heat sinks) is commonly provided to "cap" the rectifier end of the generator. In operation, the fan draws cooling air through the apertured plate, over the heat sinks and through the air flow passages within the generator assembly to exit past the fan.
It has been found that heavy duty motor vehicle generators which operate in dust-laden environments are subject to frequent breakdown which necessitates removal of the generator from the vehicle for disassembly, cleaning and/or repair and replacement in the vehicle. It is believed that such breakdowns are caused at least in part by particulate foreign matter such as dust which is drawn into the generator together with the cooling air.
For maximum cost-efficiency, heavy duty motor vehicles are often operated on a round-the-clock basis. Where the vehicles are operated in dust-laden environments, it has been found necessary to maintain a substantial inventory of replacement generators to minimize vehicle "down time" while a non-functional generator is removed and replaced with a functional generator from the inventory. Maintenance of an inventory of replacement generators implies increased costs for purchasing the replacement generators, for storing the inventory, for removing a non-functional generator from a vehicle (which entails severing of both mechanical and electrical connections between the generator and the vehicle), for mounting a replacement generator in the vehicle, and for "tearing down", cleaning and/or repairing and re-assembling the non-functional generator so that it may be returned to the inventory of replacement generators. Notwithstanding such cost, the problem of frequent breakdown has been long-standing. Manufacturers and suppliers of heavy duty motor vehicle generators have not provided a solution to the problem, although requested to do so.
The foregoing problems have been found to be particularly accentuated where heavy duty motor vehicles such as bulldozers, scrapers, trucks, loaders and the like are used in environments laden with coal-dust (e.g. open pit coal mines).
The present invention provides an air filter assembly for removing particulate foreign matter such as dust from the cooling air which is allowed to pass through a heavy duty motor vehicle generator and has been found to substantially prolong the period for which such a generator may remain in service while operating in a dust-laden environment. This implies a resultant saving in the cost of maintaining an inventory of replacement generators (since break-downs are less frequent, fewer replacement generators are required to keep a "fleet" of vehicles in operation), also implies a saving in the cost of labor required to remove, disassemble, clean and/or repair and replace non-functional generators. Vehicle "down time" is also reduced because a vehicle need not be taken out of service to interchange generators as frequently. The present invention contemplates simple maintenance at regular intervals to change the air filter element provided for use with the air filter assembly. This may be accomplished by an unskilled person since it is not necessary to tamper with any electrical connections or remove the generator from the vehicle to replace the air filter element.